The four-digit number 3,4_8 is divisible by 4.
The blank is the tens digit.
Which digit can fill the blank? (Choose the option that works.)

Divisibility by 4 depends on the last two digits, which are (blank)8. Test each option: 38 ÷ 4 = 9.5 (no), $48=4\times 12$ (yes), 58 ÷ 4 = 14.5 (no), 78 ÷ 4 = 19.5 (no). Among the options, only 4 gives 48 which is a multiple of 4, so the digit 4 works $(3,448=4\times 862)$.